Here is your equation:
[tex]6 = m - \frac{7}{8}[/tex]
You're looking for m. To find m, you have to remove everything on the same side of it. On that side, you have:
[tex]m-\frac{7}{8}[/tex]
You have [tex]-\frac{7}{8}[/tex]. To remove it, you have to do the opposite of it, which is [tex]+\frac{7}{8}[/tex]. To leave m alone, add [tex]\frac{7}{8}[/tex] to both sides.
[tex]6 = m-\frac{7}{8} \\ \\ 6 + \frac{7}{8} = m-\frac{7}{8} + \frac{7}{8} \\ \\ 6 \frac{7}{8} = m[/tex]
You have your answer, which is [tex]\bf 6 \frac{7}{8}[/tex]
If you have any questions, feel free to ask in the comments! :)